1. Field of the Invention
This invention relates to a novel method for intraoperative placement of afterloading catheters for post-operative radiotherapy.
2. Prior Art
The role of local radiation therapy, also known as brachytherapy, is supplemental to external beam radiation therapy. External beam radiation therapy is largely limited by tolerance of normal tissues such as the spinal cord, lungs, heart, skin, soft tissue, and bones in the treated area. When brachytherapy is used in conjunction with external beam therapy, a tumor bed dose can be safely boosted up to 8,000 rads.
In a report by McCaughan, 54 patients with chest wall invasion by non-oat cell carcinoma of the lung were examined (McCaughan et al., "Chest Wall Invasion in Carcinoma of the Lung", J. THORAC CARDIOVASC SURG, 89:836-841 (1985)). Six of the 54 patients had microscopic disease at the surgical margin without gross residual tumor. Three of these patients received external beam radiation and three did not. One patient in each group developed a local recurrence. Recognition of the limitations of surgical resection and conventional external beam radiation therapy in preventing local recurrence and its failure to improve survival has led to trials of perioperative brachytherapy. The technique for delivering thoracic brachytherapy was originally developed by Henschke and most recently described by Kitagawa (Henschke et al., "Interstitial Implantation of Radioactive Seeds During Thoracotomy", Lung Cancer, a Study of Five Thousand Memorial Hospital Cases, 323-346 (C.V. Mosby Co. 1968); and Kitagawa et al., "Afterloading Technique for Interstitial Irradiation of Lesions in Deep-Seated Organs", RADIOLOGY 143:543-547 (1982)). Hilaris in a pilot study of 88 patients utilized permanent Iodine-125 implantation for the unresectable primary lung lesion, temporary mediastinal Iridium-192 implantation via afterloading catheters, and post-operative external beam radiation (Hilaris et al., "Intraoperative Radiotherapy in Stage I and II Lung Cancer", SEM SURG ONC 3:22-32 (1987)). Mediastinal and local regional control was observed in 76% of the 88 patients at a twenty-six month median follow-up. He suggested that combined external beam therapy and local therapy of 6,000 rads or more would control 60-75% of the bulky tumor and 85% of patients with microscopic residual.
In the past, the placement of the small individual afterloading catheters used in thoracic brachytherapy required a time-consuming process of multiple chest wall punctures through areas of the chest wall poorly accessible when the patient lay in the lateral decubitus position. Also there is limitation of access to the thoracic cavity and mediastinum because of the displacement by the expanding and contracting lung and rib cage movement. The standard technique of directly inserting 17 gauge afterloading catheters is particularly limited by later crimping when the catheters are inserted at more lateral sites to achieve chest wall brachytherapy as opposed to treatment of the more fixed mediastinal strictures as described by Hilaris. When crimping does occur, it often prevents subsequent delivery of the radioactive source.